In chapter 23 of FlashForward, the main character Theo (Not Lloyd, I don't care what the author intended, he is a dipshit) goes to Toronto and the book talks about how a bridge was built to accommodate a subway decades before they got their first subway, there is a grocery store called Loblaws which specialize in a line of products called President's Choice, and the TTC stands for Toronto Transit Commission. This has nothing to do with the plot and feels quite forced and out of place, especially considering every other time the characters visit a foreign city nothing like that happens. I think the author relized the story was taking place in his hometown so he wanted to talk about it...but nobody cares.
A close second was in a book series that I read as a kid, Animorphs. In one of the later books one of the main character's parents (who is possessed by an alien) is about to be executed by the aliens but the titicular Animorphs launch a rescue mission. This makes sense, but what doesn't make sense is: Why was the execution to take place on earth, they had to transport her there for the execution to take place? Why not another planet-any planet!? It's never explained and feels like forced fan service. Because you know the fans wanted Marco to be reunited with his mommy. Even when I was 12 I thought that was bullshit. They should have just killed her off.